x=[0.50 ,	0.55 ,	0.60 ,	0.70 	,0.80]
y=[0.51075 ,0.59815,0.69675,0.78811,0.92652]
var=float(input())
arr=y

for j in range(1,len(x)): #5:1~4
    for i in range(len(x)-1,j-1,-1): #1
        arr[i]=(arr[i]-arr[i-1])/(x[i]-x[i-j])

ans=y[0]
for i in range(1,len(x)):
    t=arr[i]
    for j in range(i):
        t*=(var-x[j])
    ans+=t
print("%.2f"%ans)